Ruby

Ruby
Naitural ruby crystals frae Winza, Tanzanie
General
Category	Mineralvariety
Formula (repeatin unit)	aluminium oxidewichromium,Al2O3:Cr
Creestal seestem	Trigonal(Hexagonal Scalenohedral), symbol (−3 2/m),space groupR3c
Identification
Colour	Reid, mey be brounish, purplish, or pinkish
Creestal habit	Varies wi locality. Terminated tabular hexagonal prisms.
Cleavage	Na true cleavage
Fractur	Uneven or conchoidal
Mohs scalehaurdness	9.0
Skinkle	Vitreous
Streak	white
Diaphaneity	transparent
Speceefic gravity	4.0
Refractive index	nω=1.768–1.772 nε=1.760–1.763
Birefringence	0.008
Pleochroism	Orangey reid, purplish reid
Ultravioletfluorescence	reid unner longwave
Meltin pynt	2044 °C
Solubility	none
Major varieties
Sapphire	Ony color except shades o reid
Corundum	various colors
Emery	Granular

Arubyis a pink tae bluid-reid colouredgemstane,a variety o themineralcorundum(aluminium oxide). The reid colour is caused mainly bi the presence o the elementchromium.Its name comes fraeruber,Laitinfor reid. Ither varieties o gem-quality corundum are criedsapphires.The ruby is considered ane o the fowerprecious stanes,thegither wi thesapphire,theemerald,an thediamond.

Prices o rubies are primarily determined bi colour. The brichtest an maist valuable "reid" cried bluid-red, commands a lairge premium ower ither rubies o seemilar quality. Efter colour follaes clarity: seemilar tae diamonds, a clear stane will command a premium, but a ruby wioot ony needle-likrutileinclusions mey indicate that the stane haes been treatit. Cut ancarat(wicht) are an aa an important factor in determinin the price.